1. Field of the Invention
The present invention relates to a webbing take-up device that configures a vehicle seat belt device.
2. Related Art
Webbing take-up devices are known that are provided with a clutch wherein clutch weights deploy due to centrifugal force, allowing rotation of a motor to be transmitted to a spool (see Japanese Patent Application Laid-Open (JP-A) No. 2005-324772). Further, clutches are configured such that reverse direction rotation of the motor is transmitted to the spool, and configured such that forward direction rotation of the motor is not transmitted to the spool.
However, the centrifugal force imparted to the clutch weights depends on the revolution speed of the clutch weights themselves. As a result, the load imparted to a connection-disconnection mechanism that receives the force of the clutch weights deploying and transmits rotation of the motor to the spool also depends on the revolution speed of the clutch weights themselves.
Moreover, when the motor rotates the clutch weights deploy due to their own centrifugal force regardless of the rotation direction thereof. Namely, the clutch weights deploy due to their own centrifugal force even when there is no need for the clutch weights to deploy (even when the motor rotates in a forward direction).
Target values for the durability of a clutch configured including clutch weights are set giving consideration to the number of times that the clutch weights deploy.